This application is for the continued funding of a predoctoral training program in cellular and molecular biology. Since its inception in 1975, the goal of the program has been to provide trainees with both a strong intellectual foundation through coursework and also rigorous experimental training in research areas that take molecular and mechanistic approaches to a broad range of basic biological questions. Students and faculty participating in this training program are from several departments at Yale University, including the main undergraduate campus and the School of Medicine. Thus, the training program fosters connections that transcend departmental boundaries. Much of the research carded out by our students has clear potential relevance to human health and disease. Students supported by the training program will be in their first, second or third year of graduate school. The students arrive at Yale as members of the campus-wide Combined Program in Biological and Biomedical Sciences (BBS). They come with a range of backgrounds in biology, biochemistry, chemistry, genetics, molecular biology, mathematics and physics, and all students have had significant research experience before graduate school. During their first year, students will take courses that provide broad general knowledge in key disciplines and a conceptual grounding for critical evaluation of research design and methods. Students will also carry out research rotations in at least 3 laboratories selected according to their research interests. By the end of the first year, students will chose their thesis research advisor and affiliate with the academic department of their advisor. During the second year, academic requirements for the Ph.D. degree will be completed, including a qualifying exam in which the student prepares and defends a thesis proposal. In the third year, a thesis advisory committee will be assembled to guide each student to the completion of their Ph.D. training. Teaching experience is an essential part of training and all students teach with supervision and guidance from the faculty. The average time to graduation is 6 years.